This invention is directed to a waterbased coating composition and in particular to a waterbased coating containing an methylol (meth)acrylamide acrylic polymer and a polyurethane.
Methylol (meth)acrylamide acrylic polymers are polymers containing polymerized monomers of methylol methacrylamide or methylol acrylamide or any mixtures thereof.
Water based coating compositions useful for base coats and clear coats for automotive applications are shown in Wilfinger et al U.S. Pat. No. 4,730,020, issued Mar. 8, 1988. Waterbased dispersions of polyurethane are known as shown in Drexler et al U.S. Pat. No. 4,489,135, issued Dec. 18, 1984. Processes for preparing aqueous dispersions of acrylic polyesters are shown in Osborn et al U.S. Pat. No. 3,935,155 issued Dec. 9, 1975 and Osmond et al U.S. Pat. No. 3,935,155 issued Jan. 27, 1976. However, none of the compositions shown in the art form finishes having properties that are required in particular for finishing or repair of exterior finishes of automobiles and trucks.
To date, solvent based finishes have been used to repair and refinish the exterior of automobiles and trucks. Finishes of these solvent based compositions provided the required color match, cured at ambient temperatures, had excellent adhesion to the substrate and gave properties such as gloss, hardness, distinctness of image required for the exterior of automobiles and trucks. To reduce solvent emissions, waterbased paints were suggested for use. However, none of the known water based paints form finishes that have the necessary properties for automotive and truck use.
Waterbased color coat for color coat/clear coat finish, i.e., a finish having a pigmented colored layer and a top clear layer, for automobiles and trucks now is coming into use for the manufacturing of original equipment. To repair such a finish, it would be very desirable and usually necessary to use a waterbased finish to match the original color particularly when metallic flake pigments are present in the color coat.